Electropolymerization of the conducting polymer based biosensors and their characterization and catalytic response to biological molecules will be studied. We plan to construct the conducting polymer based biosensors by electrochemical polymerization of monomeric species, such as pyrrole in the presence of enzyme molecules in the solution. Some of the specific examples for the enzyme are glucose oxidase, galactose oxidase, choline oxidase, amino-acid oxidase, lactate oxidase, glycerol dehydrogenase, and lactic dehydrogenase which will be immobilized in the polypyrrole (PPy) film. Catalytic natures of the biosensors will be investigated by electrochemical methods such as amperometry. Characterization of the thin film biosensors will be carried out by the electrochemical methods (cyclic voltammetry, chronocoulometry, and etc.), spectroscopies (Raman, UV-visible, and fluorescence), and conductivity measurements (both ex situ and in situ conductivity measurements and the AC impedance methods). We also plan to study electrochemiluminescence (ECL) based optical immunosensors. The antigen (ex. human serum albumin) will be labeled with an aromatic hydrocarbon (ex. pyrene). The aromatic hydrocarbon labeled antigen emits luminescence by the electrochemical technique (called ECL). The amount of the antibody will be determined by observing the luminescence intensity change, which is due to the complexation of antigen with antibody. Several combinations of aromatic hydrocarbons and antigens will be examined in order to find out sensitive optical immunosensors. Biosensors are considered to have great promises in biomedical sciences for the measurement of drugs, metabolites, and other biomolecules. Development and commercialization of biosensors for both in vivo and in vitro measurements of the above substances are in great demands. The above two proposed studies are expected to provide basic information for the construction of reliable and sensitive biosensors.